panda gao gao

On the left is the wax block with the processed tumor tissue, which is then cut into thin slices (about the width of a human hair). These thin sections are then stained by different methods to allow microscopic evaluation of the cells in the tumor.

As most of you know, giant panda Gao Gao had surgery May 6, 2014, to remove his right testicle after a tumor was discovered by our veterinary staff (see Surgery for Gao Gao). Since that time, we have received a lot of questions about how Gao Gao’s diagnosis was made and what the findings mean for his long-term prognosis. In this blog I’ll tell you about our analysis of the tumor in the Wildlife Disease Laboratories of the San Diego Zoo Institute for Conservation Research and what we know about the tumor in giant pandas and other animals.

After we received Gao Gao’s testicle in the laboratory, parts of the tumor were processed and stained for examination under a microscope. From this, the veterinary pathologists gathered clues from the arrangement and distribution of tumor cells, features of individual tumor cells, and the frequency of tumor cell division and invasion into adjacent normal tissues.

This photomicrograph (taken through a microscope) shows the tumor on the right-hand side compressing the normal testicular tissue on the left.

We also used a specialized technique, immunohistochemistry, to determine if the tumor was making substances characteristic of one particular cell type or another. All of this information was synthesized to determine the tumor cell type and if the tumor was completely removed.

In Gao Gao’s case, the evidence supports a diagnosis of seminoma, which is a tumor arising from the germ or sperm-producing cells. In addition, there was no evidence in the surgically removed tissues of tumor spread beyond the testicle. In domestic animals, seminomas are common in older dogs, and they are usually completely cured by surgery. However, in other species such as humans, a higher percentage of seminomas will metastasize (spread) to other organs without additional treatment such as chemotherapy.

This high magnification photomicrograph shows a single tumor cell undergoing mitosis (cell division), a characteristic that indicates tumor growth. The dark purple material at the center of the cell is the nucleus beginning to divide.

So what does this mean for Gao Gao? The answer is that we can’t tell for certain if his tumor has been cured by surgery or if there is a small chance that it could reoccur at a later time. This is a common problem for pathologists who work with endangered animals, because very few tumors will ever be observed in these species, whereas it is easy to gather information on tumor behavior in dogs and humans where thousands of cases can be studied over time.

Despite this uncertainty, we are very hopeful that Gao Gao’s tumor will behave more like a seminoma in dogs. In 1997, a seminoma was found in 26-year-old giant panda Hsing Hsing, from the National Zoo, and treated by surgical removal. Hsing Hsing died two years later from kidney disease, and there was no evidence of any remaining tumor at his necropsy. We have had an opportunity to compare the microscopic sections of Hsing Hsing’s tumor with the samples from Gao Gao, and they are very similar.

Allan Pessier, D.V.M., Diplomate, A.C.V.P., is a senior scientist (veterinary pathologist) for the San Diego Zoo Institute for Conservation Research. Read his previous post, The Last Ones?

Update May 23, 2014: Gao Gao seems to be enjoying his keepers’ attention in his bedroom suite as he continues his recovery. He has even been soliciting neck scratches from them.

This morning, May 6, 2014, giant panda Gao Gao underwent surgery to remove his right testicle, due to the presence of a tumor. The surgery, which took about an hour, went well, and the San Diego Zoo’s veterinarians are hopeful that Gao Gao will make a full recovery. Unfortunately, due to the nature of the surgery, we do not know if Gao Gao will continue to be part of the panda breeding population. In addition to the surgery, veterinarians took the opportunity to do an ultrasound to follow up on his previously diagnosed heart condition. We are awaiting a review by experts for results of the ultrasound.

The San Diego Zoo’ Panda Team had been observing Gao Gao and Bai Yun for signs of breeding behavior over the last month. No changes in Bai Yun’s estrous behavior were noted, and in the best interest of Gao Gao’s health, the decision to perform the surgery was made. Bai Yun has reached an age where it is likely she will no longer go through a breeding cycle, and the observations seen this spring are consistent with signs seen in other aging pandas.

The Ministry of Forestry for the People’s Republic of China has been fully informed regarding the status of Gao Gao’s health and gave approval for the surgery. Officials from San Diego Zoo Global and China are expected to discuss the future of the giant panda program in San Diego before the end of 2014. No changes in the panda population at the Zoo are currently expected.

Christina Simmons is public relations manager for San Diego Zoo Global.

Update May 7, 2014: Gao Gao is recovering from his surgery in his own private quarters at the Giant Panda Research Station. Keepers report he is starting to show an interest in solid food.

Update May 8: Keepers report that Gao Gao is resting comfortably in his familiar bedroom area and showing marked improvement. He is eating bamboo and taking his medicine, hidden in apple slices, without a fuss.

Update May 9: Gao Gao now has access to the north yard, an off-exhibit area, if he’d like to get some fresh air.

Just for our blog readers, the following is an advance look at an article that will be published in the upcoming June digital issue of ZOONOOZ magazine. To see this and all our digital issues, download the ZOONOOZ app for iPad or the web reader version for your desktop, FREE!

Keeping elderly animals comfortable and healthy can entail rearranging animal groupings to avoid individuals in their golden years getting inadvertently roughed up by younger animals, providing medication for aching joints and other age-related ailments, and monitoring potential health issues with noninvasive exams. The latter requires the animal’s cooperation and can take time to train and condition the animal to go along with it. For instance, tracking the blood pressure of Gao Gao, our 24-year-old male giant panda, requires collaboration between keepers, veterinary staff, and panda. The calm competency of the staff involved and the sweet trust of the black-and-white bear are impressive!

Equipped with apples cut into bite-sized pieces, a small bucket of biscuit balls and bamboo bread, and a blood-pressure monitor attached to an extension cord, keepers and veterinary technicians got into position while I watched the procedure. Gao Gao ambled past, dapper and darling all at once, heading into the squeeze cage and eager to get down to business with a series of enthusiastic bleats and neighs (excited giant panda vocalizations). A steel sleeve, with a cutout area on the top that aligns with the bear’s forearm, was secured to the sturdy cage. Knowing that this noninvasive medical procedure entails his favorite foods, Gao Gao plunged his arm into the sleeve, grasping the metal bar at the end. “We use this sleeve to collect blood samples as well,” explained Brian Opitz, registered veterinary technician (RVT) at the Zoo, “so he knows to hold onto the bar inside the sleeve. To get his blood pressure, we just wait a few minutes for him to let go of the bar and let us place the cuff around his forearm.” All the while, Gao Gao is being hand-fed his favorite snacks, peering at us from behind those big, black eye spots.

Gao Gao is amply rewarded with tasty treats for his cooperation.

Gao Gao is a senior bear (in the wild, pandas can live up to about 20 years and up to 30 years in managed care), and keepers and vets go to great lengths to ensure he remains healthy. “Keepers put in a lot of time in training for these procedures so we can stay on top of possible medical issues without having to use anesthesia to collect bio-samples,” said Jill Kuntz, RVT at the Zoo. Over time, the grinding action of chewing thick bamboo stalks can wear down a panda’s teeth, as is the case with Gao Gao. Hence, he is given tasty little homemade biscuit balls made of dried bamboo, which he devoured with great gusto throughout the procedure.

Keepers and vets have been gathering baseline data—no one really knows what a normal blood pressure range is for a giant panda—on Gao Gao since May 2013. A few other zoos are also participating in this blood-pressure project. Every 7 to 14 days, staff gathers to collect 3 blood-pressure readings from Gao Gao, which he is agreeable to doing on either arm. “We also trained Yun Zi [Gao Gao’s son] to do this before he left for China,” said keeper Liz Simmons, “but he grabbed the blood- pressure cuff and tore it up.” Undaunted, they continued the training process, rewarding the younger bear for placing his arm in the steel sleeve while keepers peeled the Velcro apart to get him accustomed to the sound of the blood-pressure cuff. Soon, he was going along with the procedure, a skill that will surely come in handy in his homeland.

The information gained from these weekly readings will help us care for our senior bear.

Accepting the blood-pressure cuff is one of many husbandry behaviors the pandas are patiently trained to do through positive reinforcement. They also present a paw, belly, or rump to keepers, which is helpful in monitoring the animals’ health. Bai Yun, our prolific female panda, will even allow ultrasound procedures so veterinarians can monitor her pregnancies. It’s clear that the keepers are deeply committed to their charges. “We do this training for their health,” said Karen Scott, senior keeper. “That’s what we’re here for. We don’t force them.”

As the bottom of the treat bucket becomes visible, and his blood-pressure readings have been duly noted, Gao Gao calmly looks us all over. A keeper puts a few drops of rubbing alcohol on the floor, and the bear happily rolls around on it. “Usually animals balk at the scent of rubbing alcohol, but Gao Gao loves it—it’s like catnip to him,” explained Brian. It’s the ultimate treat! Gao Gao continued to rub and roll in the acrid odor, then proceeded to scent mark with his own “cologne.” With the procedure completed, he was free to mosey back out on exhibit. “We are lucky to have such an easygoing, tractable panda who allows us to do these exciting and important health procedures as he ages,” said Liz. And we are all fortunate to share the noble journey of Gao Gao’s life, quirks and all.

Did you know the San Diego Zoo has a bakery for animals? Do the animals like to eat bread with milk or hot chocolate? Well, not exactly, but there is one animal who is eating a special bread—a giant panda!

At the San Diego Zoo, our senior panda Gao Gao has some problems with his teeth, making it hard for him to eat his favorite food—bamboo. To help him continue eating bamboo, we created a type of bread which, of course, includes his favorite item.

Making a yummy bread for Gao Gao is not an easy task. It requires intensive work, commitment, and dedication. The Zoo’s Horticulture department provides the bamboo for the pandas; the Nutritional Services staff, along with keepers and volunteers, spend hours stripping leaves off branches. The leaves are then baked (dried) for 24 hours so they will be crunchy and perfect for the bread. The dried leaves are then ground up. The final product is chunky,
dried pieces of leaves that we call leaf flour.

The leaf flour is delivered to the panda kitchen, where the panda keepers make the bread. Ground primate biscuits are mixed with the leaf flour. Panda keepers adjust the amount of leaf flour they need to add to find the right consistency for the bread. They then add water. However, those ingredients are not enough to keep the dough together. To keep the shape of the bread, unflavored gelatin is added as a key ingredient. The mix is placed in a steamer for 50 minutes.

After all that, the bread is ready to be offered to our elder panda, not only for his enjoyment but to meet his nutritional needs.

Giant pandas are considered specialist animals, meaning their diet is based mainly on one item, in this case, bamboo. If a panda is not able to eat enough bamboo to meet his energy and nutritional requirements, his health can be compromised. The panda bread helps to keep our panda healthy. This daily food item will be part of Gao Gao’s diet for the rest of his life.

Many departments (Horticulture, Nutritional Services, Collections Husbandry Science), volunteers, and sometimes keepers from other Zoo areas (such as the Neonatal Assisted Care Unit), make the effort every day to supply and process the bamboo to keep Gao Gao healthy. Next time you see Gao Gao, think of how fortunate he is to have such dedicated, hard-working staff and volunteers who strive to provide him the best care.

Now that Bai Yun, Xiao Liwu, and Yun Zi are out in the main panda viewing area, our adult male panda Gao Gao will remain in the back with access to the north enclosure, which is now closed to guests. However, he can be seen on Panda Cam from time to time. What has he been up to these days? Relaxing. Gao Gao has been living the life off exhibit, getting back scratches from the keepers, enjoying his air-conditioned bedrooms, and eating to his little heart’s content. Currently, he weighs 176 pounds (80 kilograms) and is working on training projects with the keepers.

As many of you know, Gao Gao is trained for voluntary blood draws where he actually puts his arm through a metal sleeve and grabs a bar while a veterinarian shaves a patch of his arm and draws blood directly from a vein. Now, Gao Gao is being trained to accept blood pressure testing. He still puts his arm through the metal sleeve for keepers, but now they are able to put an actual blood-pressure cuff on his arm and begin squeezing his arm. Anytime we introduce a new behavior, it is important to take baby steps, but Gao Gao is proving to be a champ and is doing extremely well with this next phase in his training.

As our adult pandas get older, we’d like to get a baseline for their blood pressure. When we had Shi Shi, our previous adult male, we learned quite a bit about panda teeth. We’ve had Gao Gao 10 years now, and he has been trained to do so many other behaviors that help us take care of him, so why not plan for the future?

Bai Yun will also be a part of this training, but probably not while she has the cub with her. As a mom myself, I know that trying to focus on something while you have a kid climbing on you can be challenging!

As some San Diego Zoo guests are finding out, Gao Gao is the only panda out for viewing in the main exhibit currently (Bai Yun and her cub, Xiao Liwu continue to charm guests in the north exhibit until noon each day). As construction workers continue building Yun Zi’s artificial tree (which looks great so far!), Gao Gao has been entertaining us with his usual eating and sleeping, and a little extra movement right now.

Many of you know that Bai Yun would typically begin showing some hormonal behaviors as early as March for breeding season, and Gao Gao is letting us know that he is ready. He is currently eating more and gaining weight to show off to that gorgeous female he sees once a year. Of course he will not be breeding this year as Bai Yun is with a cub and not cycling. So the big question everyone’s been asking lately is, “What will Gao Gao do?” This year Gao Gao will just have to cope, and soon he’ll realize that he doesn’t smell a female in estrus.

As for next year’s breeding opportunities, we can’t say. To the best of our knowledge there hasn’t been a female panda to give birth over the age of 21, and Bai Yun will be 22 this coming September. We have observed an older male, Shi Shi, but watching a female for her entire breeding life has taught us so much about what is normal for Bai Yun. She is, after all, a big part of Gao Gao’s success as a breeding male—she is responsive and an amazing mother to her offspring.

Come see us soon, but do not be upset if you see Yun Zi off exhibit as his tree is being constructed!
Anastasia Horning is a panda narrator at the San Diego Zoo. Read her previous post, Pandas: The Big Boys.

As our panda cub is growing and changing on a regular basis, let’s not forget our older boys!

Gao Gao is doing well and has been eating quite a bit. Since he is getting panda bread every day, sometimes our keepers have to spice things up a bit and put either honey or applesauce on the bread to encourage Gao Gao to eat it. The panda bread is made up of bamboo that Gao Gao has rejected from previous meals, ground into a coarse powder, as well as ground leaf eater biscuits, shredded bamboo leaves, gelatin, and water. This is made by our keepers every morning just for Gao Gao and fed out to him throughout the day. Gao Gao’s bamboo is smaller in diameter compared to our other pandas’ diets, and this makes it easier for him to chew and digest.

Yun Zi is doing extremely well and is being a normal three year old. He has had quite a bit of fun scent marking his enclosure. The first few times I saw him leave a scent mark, he would mark the ground, turn around and smell it, and then continue to mark the rest of the enclosure. Of course, eating throughout the day has been a main part of his day; as he is not full grown yet, we may still see him jump up in weight.

We are all excited to be celebrating another anniversary for Gao Gao, as this is his 10th year here at the San Diego Zoo. Gao Gao likes his parties to be low-key and with his close human friends. We will be spoiling him with frozen applesauce treats, his favorite smells, and toys. He enjoys cinnamon spice, apple pie spice, and any musky scents. His favorite toys are the ones he can sleep in full of soft bedding.

At 23 years old, Gao Gao is doing quite well for his age. He is weighing a consistent 165 pounds (75 kilograms) and is still climbing like a young panda. He had a dental check up on January 8; they had to replace the bridge on his back molars. We have changed his food preparation to reduce the wear on his teeth and now offer him bamboo bread (made with bamboo ingredients). This is where he is getting most of his calories. We also pre-cut his favorite bamboo stalks into thinner and shorter pieces to make it easier for him to chew.

As to Gao Gao’s famous webbed feet, just his rear paws have the webbing, which is a little longer than the webbing we have between our fingers and is not noticeable unless he has a veterinary exam. He is also famous for the long hair on his rear paws: we call them his slippers.

We are happy for Gao Gao to reach this milestone in his life. He has been an exceptional mate to Bai Yun and is the father of five cubs. He continues to amaze us with how smart he is and with his gentle nature. All of his cubs have followed in his footsteps. And personally, I would say that Xiao Liwu is most like his father. So here’s to 10 great years with Gao Gao and, hopefully, many more to come!

Jennifer Becerra is a senior keeper at the San Diego Zoo. Read her previous post, Thankful for Panda.

The keepers at the San Diego Zoo are dedicated to enriching our animals’ lives and challenging them to exhibit their best abilities on a daily basis. A very common way of exercising our pandas’ sense of smell is to add new smells to their exhibit. Recently, one of the keepers added rosemary powder to the exhibit, and it certainly paid off for our Panda Trek visitors. Yun Zi constantly rolled in the powder and covered his entire body. Not every scent will inspire this same reaction; in fact, if the panda doesn’t like the scent at all, quite often they will completely ignore it and move on to other enrichment in the exhibit.

Keepers are always excited to have new scents and spices to try with their animals. Gao Gao had a lot of fun with apple-pie spice: he wore himself out rolling in it and fell asleep in the spice that the keeper had put out for him. Gao Gao is one of our toughest critics regarding what scents we put out and often shows that he prefers a stronger, rather than subtle, smell.

Yun Zi: How much longer will his hammock last?

Another way our keepers keep the animals busy is changing the exhibit, and sometimes the animals themselves let us know that an object in their exhibit needs to go. On Thursday, December 6, Yun Zi was climbing around on his logs right before his final feeding of the day. He was being his normal, active self, and decided to bounce on part of his climbing structure, breaking the end off! Being a bear, Yun Zi is very good at figuring out how to change things in the exhibit and even move them around. Our keepers have come to know that when cleaning up after Yun Zi, you really don’t know what to expect on a daily basis.

Anastasia Horning is a panda narrator at the San Diego Zoo. Read her previous post, Nighttime Pandas.

Note: Plans are underway for the installation of Yun Zi’s artificial tree, which many of you helped to fund. That should happen in just a few months!

After a good recovery from exploratory surgery on October 6, our giant panda Gao Gao is back in the main panda viewing exhibit at the San Diego Zoo and doing very well. For those of you who follow the giant pandas at the Zoo in person or online, I know that there was much anticipation about when he would be back on exhibit. I’m happy to report that he’s doing very well!

Gao Gao spent that first morning roaming his exhibit scenting the walls, trees, and rocks to cover up son Yun Zi’s scent. The first day he really just spent readjusting to being outside for longer periods of time and not having a keeper right outside the door keeping a careful eye on him. In no way was he uncomfortable or uncertain of himself on this first day, and he got back to eating and taking it easy rather quickly.

As I was narrating for panda viewers that morning when he first came out, I watched him and listened for any vocalizations that he would make. I’m happy to report that he really had no stress his first day back, and our guests were so happy to see him. For now he will be eating more leafy bamboo that has a thin stalk, meaning that our keepers are breaking the bamboo into smaller pieces for easy chewing and easy digesting.

We are very happy to have him back on exhibit and encourage you to come take a look over the next few weeks and say hello!
Anastasia Horning is a panda narrator at the San Diego Zoo. Read her previous post, Rain for Pandas.